Terminal commando
diskutil partitionDisk (zonder verdere parameters) zegt (in OS X 10.10.3):
Usage: diskutil partitionDisk MountPoint|DiskIdentifier|DeviceNode
[numberOfPartitions] [APM[Format]|MBR[Format]|GPT[Format]]
[part1Format part1Name part1Size part2Format part2Name part2Size
part3Format part3Name part3Size ...]
(Re)Partition an existing disk. All volumes on this disk will be destroyed.
Ownership of the affected disk is required.
For the partition scheme parameter:
APM specifies that an Apple Partition Map scheme be created.
MBR specifies that a DOS-compatible format scheme be created.
GPT specifies that a GUID Partitioning scheme be created.
APMFormat and APMScheme are synonyms for APM; the same applies to the others.
For each partition triplet:
Format is normally the file system personality used to set the
partition type and to choose the initialization (newfs) program.
"diskutil listFilesystems" shows a list of supported personalities.
Alternatively, you can specify "Free Space" to leave a gap.
Or you can explicitly specify the partition type (either as a human-
readable string or as a GPT UUID constant) surrounded by "%".
Explicitly specifying the type or Free Space implies %noformat% (below).
Name is the initial volume name (subject to file system-specific naming
restrictions). You can also specify %noformat% to skip initialization
(newfs). If the format (above) is "Free Space" or an explicit partition
type, the name is ignored, but it must still be present.
Size is the length of the partition (slice); the exact resulting size may
be somewhat larger or smaller as necessary in certain cases.
Valid sizes are floating-point numbers with a suffix of B(ytes), S(512-byte-
blocks), K(ilobytes), M(egabytes), G(igabytes), T(erabytes), P(etabytes),
or (%)percentage of the total size of the whole disk; also, at most 1 triplet
can specify a size of "R" (without a preceding number) to specify the remainder
left on the whole disk after considering the other sizes.
The last partition will be lengthened to the end of the disk; to specify an
exact size for the last usable partition, specify an additional partition
of type "Free Space".